1. Field of the Invention
The present invention relates to a substrate processing apparatus, particularly a single-substrate type substrate processing apparatus, and a substrate processing method spraying gas to a semiconductor substrate, a glass substrate for a liquid crystal display, a glass substrate for a photomask, a substrate for an optical disk or the like (hereinafter simply referred to as “substrate”) for drying the substrate.
2. Description of the Background Art
A single-substrate type substrate processing apparatus supplying a chemical solution such as hydrofluoric acid to a substrate while rotating the same for etching or cleaning the substrate generally performs rinse processing with deionized water after the chemical solution processing, followed by drying processing for removing the deionized water adhering to the substrate. In general, such a substrate processing apparatus dries the substrate by a technique of rotating the substrate thereby spinning off the same as proposed in Japanese Patent Application Laying-Open Gazette No. 11-233481 (1999), for example.
In order to dry a large substrate such as a substrate for a liquid crystal display, the so-called air knife may be employed for spraying stratified gas from a slitlike discharge port to the surface of the substrate, as proposed in Japanese Patent Application Laying-Open Gazette No. 11-111666 (1999), for example.
In a drying step subsequent to the rinse processing with deionized water, however, imperfect drying may result in the form of water marks, which are readily caused particularly when the substrate processing apparatus etches silicon (Si) or polysilicon forming the surface of the substrate with hydrofluoric acid due to partial exposure of a hydrophobic surface. Oxygen contained in the atmosphere may conceivably be dissolved into moisture adhering to the surface of the substrate and react with Si to result in residues, which in turn form such water marks due to drying.
In order to prevent formation of such water marks, IPA (isopropyl alcohol) may be sprayed to the surface of the substrate in the drying processing for replacing the moisture with IPA. According to this method, however, combustible IPA is handled in the form of a liquid or gas, and hence the apparatus must be brought into an explosion-proof structure in consideration of safety. In view of the process, the conditional range for replacing the residual moisture with IPA is so narrow that reproducibility for prevention of water marks is hard to attain. When the organic IPA is supplied to the surface of the substrate in the final drying step, increasingly refined device characteristics may disadvantageously be deteriorated.